High Speed Rotors on Gas Bearings: Design and Experimental Characterization

Belforte, Guido; Colombo, Federico; Raparelli, Terenziano; Trivella, Andrea; Viktorov, Vladimir

doi:10.5772/50795

Cited by 6 publications

(4 citation statements)

References 25 publications

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“…It is also reported that GFBs can operate even at a high speed of 500 kr/min. 3,4 In 1994, Heshmat 5 achieved a breakthrough maximum pressure of 6.735 bar at 59.7 kr/min rotational speed while designing foil bearings. The use of gas bearings in the field of turbomachinery led several researchers to propose different types of foil bearings to improve load-carrying capacity.…”

Section: Introductionmentioning

confidence: 99%

Influence of slip-flow phenomenon on thermohydrodynamic behaviour of gas foil thrust bearings

Kumar

Khamari

Behera

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part J:

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Gas foil bearings are often used in high-speed turbomachinery such as turboexpanders and turbochargers due to their merits over simple gas-lubricated bearings. The merits of gas foil bearings include their ability to tailor dynamic parameters such as stiffness and damping. Gas foil bearings usually have low clearance and operate at a high rotational speed, which eventually leads to velocity slip at the solid–fluid interface. This article investigates the effect of slip flow on various parameters of gas foil thrust bearings. A numerical model is formulated to predict pressure, film thickness and temperature distribution of helium lubricated gas foil thrust bearing at high rotating speed. The Reynolds equation is modified by assuming first-order slip coupled with the structural (compliant) and energy equation. The temperature-dependent viscosity and density of the fluid are also considered in the Reynolds equation to predict the thermohydrodynamic behaviour of gas foil thrust bearings. The numerical model thus developed uses a finite-difference method and the Newton–Raphson method to solve the Reynolds equation,whereas the successive over-relaxation method is used to solve the energy equation. Various performance parameters are compared for slip and no-slip conditions for gas foil thrust bearings. The results show a considerable difference between the two phenomena. Also, the conventional Reynolds equation tends to overestimate the load-carrying capacity.

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Section: Introductionmentioning

confidence: 99%

Influence of slip-flow phenomenon on thermohydrodynamic behaviour of gas foil thrust bearings

Kumar

Khamari

Behera

et al. 2021

Proceedings of the Institution of Mechanical Engineers, Part J:

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“…The exceptional advantages of aerostatic bearings are the high rotation speed and extremely low friction [1][2][3][4][5]. The bearings are lubricated with compressed gas from the source into the flow path, which usually uses passive elements to limit the gas flow to create a certain pressure which is necessary to maintain the current load and to control the displacement of the moving part of the structure, thereby ensuring its stiffness [4][5][6][7][8][9][10][11][12][13][14][15][16]. And although the development of technology has contributed to the improvement of bearings, they still have a drawback-low stiffness [8,10,17,18].…”

Section: Introductionmentioning

confidence: 99%

Mathematical Modeling on Statics and Dynamics of Aerostatic Thrust Bearing with External Combined Throttling and Elastic Orifice Fluid Flow Regulation

et al. 2020

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As aerostatic bearings are used in high-speed metal-cutting machines to increase machining accuracy, there is the need to improve their characteristics, including compliance, which is usually high. In practical applications, a significant reduction of bearing compliance is often necessary, sometimes down to zero and even negative values, to ensure automatic compensation of the elastic deformation in the machine technological system. A decrease in compliance leads to deterioration in the dynamic performance of the bearing, so it is necessary to develop new designs that meet the above requirements. This article considers an aerostatic bearing, in which decrease in compliance is ensured by the use of air throttling with elastic orifices. To ensure its stability, the principle of combined external throttling was applied, which can substantially improve the dynamics of conventional aerostatic bearings. A mathematical model of the elastic orifice deformation was developed, together with the flow rate performance calculation method. The method ensured full qualitative and satisfactory quantitative agreement with the experimental data. The model was used in the mathematical modeling of the aerostatic bearing movement. The article also proposes a method to calculate the static load capacity and compliance of a bearing, as well as a numerical method for fast computation of its dynamic performance, which allows for real-time multi-parameter optimization by the bearing dynamic performance criteria. The study showed that there is an optimal set of design parameters for which low, zero, and negative static compliance of the bearing is ensured, with the necessary stability margin, high speed, and the non-oscillatory nature of the transient processes.

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“…However, the evolving design of the gas foil bearings (GFBs) has improved the dynamic characteristics of the gas bearings, enhancing its scope of application. The GFBs are capable of operating at a speed over 500 krpm [3,4]. Gas foil journal bearings (GFJBs) and gas foil thrust bearings (GFTBs) are used to bear radial loads and axial loads, respectively, developed in the rotor of the turboexpander.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of slip flow phenomenon on performance characteristics of gas foil journal bearing

et al. 2020

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Gas foil bearings (GFBs) are often employed in turbomachinery, particularly in high-speed turbochargers and turboexpanders. These bearings operate at very high speed and under very low clearance. On account of very low clearance, velocity slip can be observed at the gas-solid-interface. This paper investigates the effect of slip on various performance characteristics of the GFB. A model is put forth to predict the pressure and film thickness of a Gas Foil Journal Bearing (GFJB) used in helium-liquefaction turboexpander operating at 240 krpm. The present model addresses the slip at the gas-foil interface. Modified Reynolds equation, assuming first-order slip, is used along with the structural equation, which illustrates the compliant property of the foil. A numerical model is developed by finite difference approximation and solved by an iterative method. Various performance parameters are assessed for the no-slip and slip flow phenomenon in GFJB. The results are compared and a considerable difference is seen between the two models. The conventional Reynolds equation overestimates the load by approximately 8% at 240 krpm. The load-carrying capacity at different values of Knudsen number is also shown.

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High Speed Rotors on Gas Bearings: Design and Experimental Characterization

Cited by 6 publications

References 25 publications

Influence of slip-flow phenomenon on thermohydrodynamic behaviour of gas foil thrust bearings

Influence of slip-flow phenomenon on thermohydrodynamic behaviour of gas foil thrust bearings

Mathematical Modeling on Statics and Dynamics of Aerostatic Thrust Bearing with External Combined Throttling and Elastic Orifice Fluid Flow Regulation

Numerical investigation of slip flow phenomenon on performance characteristics of gas foil journal bearing

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